Unmarried couples in Australia who are considered to be in a de facto relationship are subject to settlement provisions should they break up.

And it's not always a fair outcome for both parties.

"A prenup is important when people come into a relationship with significant wealth, because they often get screwed over.

"The thing people don't understand is that just because you come in with more, doesn't mean you leave with more. You don't get credit for your contributions. It gets watered down with the passing of time."

For the person who earns less, the settlement is adjusted and "they get more out of the pot", she said.

Prenuptial agreements are gaining in popularity — particularly among parents who want their kids to be safe. Picture: iStock

De facto relationships are subject to a two-year rule - meaning you have to live together for at least that time before it applies. But there are ways around it, Ms Shevket said.

"I wouldn't let him leave a toothbrush at my place. There was a bit of mould on the wall in the corner of the room and he wanted to fix it up and paint it for me.

"But I wouldn't let him because de facto status can apply if you've made contributions to the other person's property."

Fidan Shevket says there’s a fine line between love and hate.

For Ms Shevket and her partner, the agreement is about ensuring they're "on the same page" and to avoid any conflict down the track.

"The agreement talks about the payout, our assets and belonging, a spousal maintenance clause … it's also very specific about my stuff," she said.

It includes kitchenware, linen, kitchen appliances and obviously the big stuff like shares and real estate.

"I'm a collector of things too. I have a significant Superman collection. I have heaps of stuff from Marlon Brando, Christopher Reeve … lots of statues and figurines. I've got a whole room dedicated to Superman.

"I've got a designer shoe collection worth probably $30,000. Not that he's going to take the shoes."

And he was understanding about her position, Ms Shevket said - just as a growing number of Australian couples are.

People who are entering second marriages or who have children from a previous relationship are also fond of prenups, Fidan Shevket says.

More often than not, it's parents of one of the partners in the couple that wants an iron-clad protection of family wealth, she said.

"Their kids might be set to come into a lot of money through inheritance. You can quarantine that.

"People who are getting married for a second time are also more realistic about it. People who have kids from another relationship are also keen to protect their children's financial futures."

Last night's episode of Insight heard from a number of couples about their prenup experiences, including Kathy and Cam Robinson.

He had more assets and multiple properties, so they discussed an agreement early on in their relationship. Ultimately, they decided against signing one.

"Going into a relationship you have to have trust," Ms Robinson said. "If you can't trust your partner, then who can you trust really?"